Threats
Photo: Glenn Jacobson
© 2008 Australian Antarctic Division
Kingston Tasmania 7050
Toothfish
The Antarctic toothfish is a key predatory fish species in the Ross Sea. It is the largest fish by far, reaching lengths of more than 163 cm and weights of more than 70 kg.
An adult toothfish produces many young, but only a tiny fraction of these will become adults themselves. The few young fish that do survive beyond the sub-adult stages are slow to develop – estimated at less than an 2 cm and 1 kg per year – taking at least 8-12 years to become sexually mature. But once grown, the fish can live more than 50 years, giving it more than 35-40 years to reproduce, but individual fish do not reproduce every year.
Because of this lifecycle strategy, each adult fish has a disproportionately high value to the population. The toothfish has been called the most voracious predatory fish in the Southern Ocean, in a sense, occupying the place of sharks in other systems.
Toothfish in the Market
But the Antarctic toothfish is also a delicacy. Both Antarctic and Patagonian toothfish are sold in restaurants around the world. They are not called by their real name. Toothfish is known as the more-marketable Chilean Sea-Bass in the United States, Merluza Negra in Chile, Argentina and Uruguay, and Mero in Japan.
The Patagonian toothfish has been drastically overexploited in much of the more northern Southern Ocean. Its decline is well documented. The overwhelming demand for and dwindling supply of the fish have resulted in sky-high prices, with reports of up to $3,000 for a single toothfish. In essence, finding one of the last pockets of toothfish is now like unearthing buried treasure. The Ross Sea is one of the last such pockets.
Fishing in the Ross Sea
Since 1996, industrial fishing, initially from New Zealand but now including a dozen nations, has targeted the Antarctic toothfish in what is called fishing area 88.1 (Ross Sea and sea mounts north). Quotas for fishing are set by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR). Both CCAMLR and the fishing companies assert that this fishery has not had ill effects on the ecosystem. But they are not engaged in any monitoring to justify that statement. Initially, quotas gradually increased, largely in absence of accurate data on fish stocks and sustainable yields, and despite industry claims, recent reports indicate that in just 12 years the industry’s impact is already evident.
The allowable catch increased annually during the first 7 years and then stabilized at ~3,200 tons of fish in the 2002/2003 (December – March) season, and in a given year, 10-20 large ocean-going vessels are now involved. As the industry has grown, it has become more and more difficult for scientists at the southern edge of the species’ range, in McMurdo Sound, to catch toothfish.
In the 30 years prior to the fishery, scientists caught 200-500 fish per season, depending on how much time was available. (Almost all fish were tagged and released). Using 1987 as an example, it took a scientist approximately 73 hours of effort (i.e. soak time), with a single hook, to catch an adult toothfish. In 2007, after 12 years of industrial fishing, it took 1,800 hours of effort with a single hook, making it 25 times more difficult to catch a toothfish for study.
But how could these observations exist concurrently with an expanding, supposedly sustainable industry? Obviously, if it were now 25 times harder for the industry to catch a toothfish, the fishery would stop for purely economic reasons. The answer lies in the distribution of toothfish in the Ross Sea.
The largest concentration of toothfish lives at the northern edge of the Ross Sea, along the dropping slope of the continental shelf. This is the best toothfish habitat, as upwelling along here leads to a very productive stretch of ocean. It is, not surprisingly, where the fishing boats fish. The toothfish range extends southward across the Ross Sea shelf and into McMurdo Sound, where the scientists have fished. But toothfish caught and tagged in McMurdo Sound have been caught in the industrial fishery along the continental slope and beyond, indicating that it is all one population.
Competition for space and food in the best habitat along the slope forces some portion of the toothfish to search out less ideal habitat further south in the Ross Sea, as well as to the north. But as fishing depletes the population along the slope, in the core of the stock, the best toothfish habitat opens up again and the periphery of the population contracts towards its center.
The industry has not yet felt the impact of its own fishing because their fishing grounds are still flush with fish; the catch per unit effort of the fishery has remained about constant. But the fishing is quickly draining the population. By the time the industry does feel the impact of its own fishing, it will be too late for the rest of the Ross Sea. The marine community will already be adjusting to the loss of a key member.
The drastic decline in effectiveness of scientific fishing in the southern Ross Sea is the proverbial canary in the coalmine. It is an indication that the industry is already having significant effect in the Ross Sea, and whether an animal eats toothfish, is eaten by toothfish, is eaten by what the toothfish eat, or competes with toothfish for food, the disappearance of toothfish will have an impact. Thus the balance of the entire system will change. Elsewhere in the World Ocean similar stories have played out countless times, with the over-fishing of tuna, cod, groupers, and sharks, just to name a few.
Whaling
In addition to building pressure from the toothfish fishery, the Japanese Research Program in Antarctica (JARPA) continues to take minke whales from the Ross Sea and vicinity, recently having increased its relatively low ‘scientific’ catch to levels seen in the industrial era.
Commercial whaling took place in the Ross Sea region from 1923 until 1986, when public recognition of the extreme pressure on worldwide whale stocks spurred an international moratorium on whaling.
The best evidence suggests that the current whale biomass in the Southern Ocean is less than 10% of that in 1900. But since the great whales, like blue, fin and sei whales, which suffered the brunt of the industry, rarely utilized the Ross Sea shelf, the drastic decline probably has had limited effect on the Ross Sea ecosystem.
Only the Antarctic minke whale, killer whale and Arnoux’s beaked whale have ever been abundant in waters overlying most of the shelf. Moreover, the minke whale, to which the industry turned in the 1970s and 1980s, occurs far into the ice pack where whalers do not go, thus safeguarding a ‘reserve’ population. It is the only baleen whale in the Southern Ocean that has been able to recover from whaling.
Clear and Present Danger
Despite the size and charm of the whales, it is the toothfish fishery, not JARPA that poses the most critical and immanent danger to the Ross Sea ecosystem. With the loss of such a key species, the food web will disassemble, like a house of cards. If the fishery continues on its present path, the ecosystem will pay the price, as will the fishermen, who will be out of work when the fish are gone. The only question is when, and no one really knows. But the path is not yet set. While we are truly running out of time, there is still a chance to protect the Ross Sea...